This invention relates generally to shelves for housing printed circuit packs (PCPs) and more particularly to the provision of connections for operation, administration, maintenance and provisioning functions.
Shelves for housing PCPs face significant space restrictions. This is particularly so for shelves located in a central office of a telephone switching service provider. The space available is dictated by the height, width and depth of the racks which a service provider uses for holding the shelves. It is important to minimize the space occupied by any component of a system.
A shelf typically has a printed circuit board (PCB) extending across the rear, referred to as a backplane, which has a series of connectors on its front face. Alternatively, the backplane may be placed more forwardly in the shelf and have a series of connectors on both its front and rear face. In such cases, the backplane may be referred to as a midplane. PCPs are oriented perpendicular to the backplane and plugged into the connectors on the backplane. These connectors generally have a super set of pins to match a large number of connection configurations so that a variety of different PCPs may alternatively be plugged into the same position in the backplane.
I/O connections for,carrying input and output signals to the PCPs within the shelf and connections for the control of the shelf, namely the operation, administration, maintenance and provisioning (OAMandP) of the shelf itself, are also usually made through the backplane. The type of cable connectors required for the I/O of the PCPs will vary depending on the PCPs connected to the shelf. In contrast, the number and type of connectors required for the OAMandP of a shelf supplied by a particular service provider is normally fixed.
For both I/O and OAMandP, typically a fixed pattern of cable connectors is mounted on the back surface of the backplane. Although a fixed pattern is acceptable from the OAMandP perspective, there are several disadvantages to this mode of enabling cable connections for the OAMandP of the shelf. First, access to the cable connectors is only available from the rear of the backplane. Second, the mounting of the cable connectors on the rear of the backplane means that the backplane must sit sufficiently forward in the rack to accommodate their presence. This limits the usable depth of rack and, by extension, the width of the PCPs which may be plugged into the backplane. Third, placing the cable connectors on the rear of the backplane prevents the backplane from being used in the midplane configuration. Forth, if there were a fault found with one of the OAMandP connectors, the entire backplane would need to be replaced.
One solution which has been proposed by Murphy et al. is described in U.S. Pat. No. 5,769,644. In that solution, both the I/O connections for the PCPs in the shelf and the connections for the OAMandP are done through a module which extends outward from the side of the shelf. This module can be exchanged with other connector modules where a change in the PCPs in the shelf necessitates a change in the I/O connectors. This removes the cable connectors from the rear of the backplane and allows more flexibility to change PCPs without needing to change the backplane. However, because the OAMandP connectors are on the same module, the change in the I/O connectors also results in an unnecessary change in the OAMandP connectors. Also, the module is in a fixed position relative to the shelf.
The present invention is directed to an improved shelf for housing PCPs. A backplane extends across the shelf. A connector module having the OAMandP connectors is electrically connected to the backplane and has two positions. In one position it extends sideways from the shelf with the connectors facing either forward or backward, depending on the user""s preference. This allows the user front or rear access for connection to the connectors of the module. In the second position, the OAMandP connector module is substantially flush with the side of the shelf. This position allows the OAMandP module to be tucked out of the way to minimize the space used by the OAMandP module and allow access to what is behind it along the side of the shelf.
Advantageously, the OAMandP functionality is on a separate module which may be changed or left unchanged irrespective of any changes made to other connectors in the system.
Also advantageously, if used in conjunction with a system that removes the I/O connectors from the backplane, the backplane may sit more rearwardly in the shelf, and thus the size, and consequently the functionality, of the PCPs which connect into the backplane may be increased. Alternatively, the backplane may be used in a midplane configuration.
Further, the dual positioning allows for easy access to connect to the connectors of the OAMandP module while allowing the OAMandP module to be tucked out of the way when new connections are not being made.